The association between body roundness index and osteoporosis in older patients: a cross-sectional study based on a comprehensive geriatric assessment.

BACKGROUND: As an age-related bone disease, osteoporosis poses a serious threat to the lives and health of the elderly. The Body Roundness Index (BRI) is a physical indicator for assessing obesity, particularly abdominal obesity, which can describe human body morphology more accurately than body mass index (BMI). This study aims to investigate the association between BRI and osteoporosis in elderly hospitalized patients. METHODS: We enrolled 620 elderly patients (≥ 60 years) from the Cadre Ward of the First Hospital of Jilin University. Osteoporosis was diagnosed using ultrasonic bone densitometry, and the body roundness index (BRI) was calculated based on waist circumference and height. Multivariate logistic regression models were applied to assess the association between BRI and osteoporosis. Restricted cubic splines (RCS) were applied to evaluate their potential nonlinear relationships, while threshold effect analysis-performed through piecewise logistic regression-was used to identify potential break-point. Subgroup analyses (stratified by age, sex, smoking, alcohol use, ADL, fall risk, and nutritional status) were conducted to confirm the robustness and consistency of the findings. RESULTS: The study cohort comprised 620 elderly participants (mean age: 74.67 ± 8.93 years), of whom 202 (32.6%) were diagnosed with osteoporosis. Multivariable-adjusted logistic regression revealed a significant positive association between body roundness index (BRI) and osteoporosis risk (OR = 1.587, 95% CI: 1.299-1.940; p < 0.001). Restricted cubic spline analysis demonstrated a J-shaped curvilinear relationship. Threshold effect analysis identified a break-point at BRI = 4.67; Below this threshold, BRI was not significantly associated with osteoporosis risk (OR = 0.920, 95% CI: 0.67-1.263, P = 0.606). Above the threshold, each 1-unit increase in BRI was associated with a 178.9% higher odds of osteoporosis (OR = 2.789, 95% CI: 1.831-4.247, P < 0.001). Stratified analyses consistently supported BRI-osteoporosis associations across demographic and clinical subgroups. CONCLUSIONS: This cross-sectional study identifies BRI as an independent anthropometric predictor of osteoporosis in older adults (age ≥ 60 years), characterized by a nonlinear J-shaped dose-response pattern. The observed break-point (BRI = 4.67) suggests a critical threshold for accelerated osteoporotic risk. The robustness of associations across heterogeneous subpopulations, persisting after comprehensive confounder adjustment, positions BRI as a novel and clinically relevant biomarker for osteoporosis risk stratification in geriatric populations.